The primary objective of this work is to develop a simple and safe postcoital contraceptive method by means of subcutaneous or oral administration of oleanoglycotoxin-A. Ideally, the ability of this compound to prevent pregnancy would not be restricted to its administration immediately after unprotected coital exposure but would also be effective after an extended period of time following exposure even after blastocyst implantation has occurred. Although not intended for frequent use, ideally the technique could be used repeatedly, if necessary, without immediate or long-term risk to health or fertility.